Lebell, the matter you are referring to, called 'reserved powers' is addressed in the Tenth Amendment.
However, in the larger issue of state versuses national power, the established precedent is indeed national supremacy.
For instance, in the case of McCulloch v. Maryland, the Supreme Court held that states could not deliberately interfere with the institutions of the federal government (here the matter at hand was whether a state could tax a federal bank.) This decision is still debated today in various forms.
As I understand it (and I'm no expert) the situation today between the national and state governments is arranged according to the principles of 'cooperative federalism' which means powers can be shared by the respective governments (each has the power to tax, and so on).
I'm not sure, however, how that would apply to the sweet leaf.
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The tragedy of life is what dies inside a man while he lives.
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